Characterization of gene expression associated with the adaptation of the nematode C. elegans to hypoxia and reoxygenation stress reveals an unexpected function of the neuroglobin GLB-5 in innate immunity

Oxygen (O₂) is a double-edged sword to cells, for while it is vital for energy production in all aerobic animals and insufficient O₂ (hypoxia) can lead to cell death, the reoxygenation of hypoxic tissues may trigger the generation of reactive oxygen species (ROS) that can destroy any biological molecule. Indeed, both hypoxia and hypoxia-reoxygenation (H/R) stress are harmful, and may play a critical role in the pathophysiology of many human diseases, such as myocardial ischemia and stroke. Therefore, understanding how animals adapt to hypoxia and H/R stress is critical for developing better treatments for these diseases. Previous studies showed that the neuroglobin GLB-5(Haw) is essential for the fast recovery of the nematode Caenorhabditis elegans (C. elegans) from H/R stress. Here, we characterize the changes in neuronal gene expression during the adaptation of worms to hypoxia and recovery from H/R stress. Our analysis shows that innate immunity genes are differentially expressed during both adaptation to hypoxia and recovery from H/R stress. Moreover, we reveal that the prolyl hydroxylase EGL-9, a known regulator of both adaptation to hypoxia and the innate immune response, inhibits the fast recovery from H/R stress through its activity in the O₂-sensing neurons AQR, PQR, and URX. Finally, we show that GLB-5(Haw) acts in AQR, PQR, and URX to increase the tolerance of worms to Pseudomonas aeruginosa pathogenesis. Together, our studies suggest that innate immunity and recovery from H/R stress are regulated by overlapping signaling pathways.

Fecal immunochemical tests compared with guaiac fecal occult blood tests for population-based colorectal cancer screening

Colorectal cancer (CRC) is the second most common cause of cancer deaths in Canadian men and women - accounting for almost 12% of all cancer deaths. In Ontario, it is estimated that 8100 persons were diagnosed with CRC in 2011, and 3250 died from the disease. CRC incidence and mortality rates in Ontario are among the highest in the world. Screening offers the best opportunity to reduce this burden of disease. The present report describes the findings and recommendations of Cancer Care Ontario's Fecal Immunochemical Tests (FIT) Guidelines Expert Panel, which was convened in September 2010 by the Program in Evidence-Based Care. The purpose of the present guideline is to evaluate the existing evidence concerning FIT to inform the decision on how to replace the current guaiac fecal occult blood test with FIT in the Ontario ColonCancerCheck Program. Eleven articles were included in the present guideline, comprising two systematic reviews, five articles reporting on three randomized controlled trials, and reports of four other studies. Additionally, one laboratory study was obtained that reported on several parameters of FIT tests that helped to inform the present recommendation. The performance of FIT is superior to the standard guaiac fecal occult blood test in terms of screening participation rates and the detection of CRC and advanced adenoma. Given greater specimen instability with the use of FIT, a pilot study should be undertaken to determine how to implement the FIT in Ontario.

A membrane-bound vertebrate globin

The family of vertebrate globins includes hemoglobin, myoglobin, and other O₂-binding proteins of yet unclear functions. Among these, globin X is restricted to fish and amphibians. Zebrafish (Danio rerio) globin X is expressed at low levels in neurons of the central nervous system and appears to be associated with the sensory system. The protein harbors a unique N-terminal extension with putative N-myristoylation and S-palmitoylation sites, suggesting membrane-association. Intracellular localization and transport of globin X was studied in 3T3 cells employing green fluorescence protein fusion constructs. Both myristoylation and palmitoylation sites are required for correct targeting and membrane localization of globin X. To the best of our knowledge, this is the first time that a vertebrate globin has been identified as component of the cell membrane. Globin X has a hexacoordinate binding scheme and displays cooperative O₂ binding with a variable affinity (P₅₀∼1.3–12.5 torr), depending on buffer conditions. A respiratory function of globin X is unlikely, but analogous to some prokaryotic membrane-globins it may either protect the lipids in cell membrane from oxidation or may act as a redox-sensing or signaling protein.

An alteration in the levels of populations of CD4+ Treg is in part responsible for altered cytokine production by cells of aged mice which follows injection with a fetal liver extract

We have shown previously that a fetal sheep liver extract (FSLE) containing significant quantities of fetal ovine gamma globin chain (Hbgamma) and LPS injected into aged (>20 months) mice could reverse the altered polarization (increased IL-4 and IL-10 with decreased IL-2 and IFNgamma) in cytokine production seen from ConA stimulated lymphoid cells of those mice. The mechanism(s) behind this change in cytokine production were not previously investigated. We report below that aged mice show a >60% decline in numbers and suppressive function of both CD4(+)CD25(+)Foxp3(+) Treg and so-called Tr3 (CD4(+)TGFbeta(+)), and that their number/function is restored to levels seen in control (8-week-old) mice by FSLE. In addition, on a per cell basis, CD4(+)CD25(-)Treg from aged mice were >4-fold more effective in suppression of proliferation and IL-2 production from ConA-activated lymphoid cells of a pool of CD4(+)CD25(-)T cells from 8-week-old mice than similar cells from young animals, and this suppression by CD25(-)T cells was also ameliorated following FSLE treatment. Infusion of anti-TGFbeta and anti-IL-10 antibodies in vivo altered Treg development following FSLE treatment, and attenuated FSLE-induced alterations in cytokine production profiles.

Identification of an immunogenic CD8+ T-cell epitope derived from gamma-globin, a putative tumor-associated antigen for juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia (JMML) is a rare clonal myeloproliferative disorder. Although allogeneic stem cell transplantation can induce long-term remissions, relapse rates remain high and innovative approaches are needed. Since donor lymphocyte infusions have clinical activity in JMML, T-cell-mediated immunotherapy could provide a nonredundant treatment approach to compliment current therapies. Gamma-globin, an oncofetal protein overexpressed by clonogenic JMML cells, may serve as a target of an antitumor immune response. We predicted 5 gamma-globin-derived peptides as potential human leukocyte antigen (HLA)-A2 restricted cytotoxic T lymphocyte (CTL) epitopes and showed that 4 (g031, g071, g105, and g106) bind A2 molecules in vitro. Using an artificial antigen-presenting cell (aAPC) that can process both the N- and C-termini of endogenously expressed proteins, we biochemically confirmed that g105 is naturally processed and presented by cell surface A2. Furthermore, g105-specific CD8(+) CTLs generated from A2-positive healthy donors were able to specifically cytolyze gamma-globin(+), but not gamma-globin(-) JMML cells in an A2-restricted manner. These results suggest that this aAPC-based approach enables the biochemical identification of CD8(+) T-cell epitopes that are processed and presented by intact cells, and that CTL immunotherapy of JMML could be directed against the gamma-globin-derived epitope g105.

[Preparation and identification of monoclonal antibodies against different epitopes on human zeta globin chain]

OBJECTIVE

To prepare and identify the monoclonal antibodies (mAb) against human zeta globin chain.

METHODS

BALB/c mice were immunized with purified recombinant zeta globin chain, and the hybridomas were generated by fusion of mouse spleen cells and myeloma cells NS-1. After three fusions and successive cloning, 3 hybridoma cell lines secreting the mAb against zeta were obtained and the antibodies were purified from the ascites, followed by identification with indirect enzyme-linked immunosorbent assay (ELISA) and sandwich ELISA in combination with rabbit anti-zeta serum.

RESULTS AND CONCLUSION

Three hybridoma cell lines secreting anti-zeta mAb were established, designated as 1A12, 3H9 and 4D11, respectively. Both of 3H9 and 4D11 mAbs belonged to IgG1 isotype and mAb 1A12 to IgG2a. All the mAbs could bind specifically to recombinant zeta and natural zeta globin from hemolysate of --(SEA) gene carrier. In addition, 1A12 and 3H9 mAbs could recognize different epitopes on zeta globin, suggesting the possibility of developing a detection system for screening alpha-thalassemia with these mAbs.

Purification of placenta-eluted gamma globulins and their strong effect against graft-versus-host reactions in vitro and in vivo

In the 1980s, attempts were made to use placenta-eluted gamma globulins (PEGG) in patients with graft-versus-host disease (GVHD) after bone marrow transplantation (BMT). Because production of PEGG had been discontinued for many years, we aimed to reestablish a method of production and further explore the mechanisms of the effect of these globulins on GVHD. PEGG were prepared by elution at acid pH from extensively washed human placenta followed by precipitation with saturated ammonium sulfate and absorption on a protein A Sepharose column. In vitro study showed PEGG significantly inhibited both the proliferative response of T-cells to phytohemagglutinin (PHA) and the mixed lymphocyte reaction (MLR). Results of flow cytometric analysis indicated that PEGG down-regulated the expression of CD25 and CD69 on T-cells stimulated by PHA. Cytokine quantification in MLR supernatant showed that PEGG decreased secretion of interferon 3 (IFN-3) but increased production of interleukin 4. In a murine GVHD model, we investigated the preventive effect of PEGG on lethal GVHD in irradiated recipients of allogeneic bone marrow cells and spleen cell transplants by in vivo administration. Compared with controls, recipients treated with PEGG had a markedly increased survival rate with less histopathological evidence of GVHD. These results suggest that PEGG may be a potent therapeutic agent for GVHD.

Analysis of interaction of cloned human and/or sheep fetal hemoglobin γ-chain and LPS in augmenting induction of inflammatory cytokine production in vivo and in vitro

We have reported earlier that purified preparations of sheep fetal hemoglobin, but not adult hemoglobin, in concert with non-stimulatory doses of lipopolysaccharide (LPS) (lipid A), act cooperatively to regulate in vitro production of a number of cytokines, including TNFalpha, TGFbeta and IL-6 from murine and human leukocytes. Following in vivo treatment of mice with the same combination of hemoglobin and LPS, harvested spleen or peritoneal cells showed a similar augmented capacity to release these cytokines into culture supernatants. We report below that genetically cloned gamma-chain of human or sheep fetal hemoglobin, but not cloned alpha- or beta-chains, can produce this cooperative effect, as indeed can HPLC purified, heme-free, gamma-chains derived from cord blood fetal hemoglobin, and that purified haptoglobin completely abolishes the cooperative interaction.

Protection studies with a globin-enriched protein fraction of Ostertagia ostertagi

The protective capacity of an adult stage Ostertagia ostertagi globin antigen was tested in four vaccination experiments in cattle. In a preliminary experiment, calves were vaccinated three times intraperitoneally with 250 microg globin in Freund's adjuvant and challenged with a trickled infection of 25,000 infective larvae. In three subsequent field studies, calves were vaccinated twice or three times intramuscularly with 80-100 microg globin in Quil A and challenged with a natural gastrointestinal nematode infection on pasture. Higher globin-specific antibody levels were detected in the vaccinated calves than in the control animals in all vaccine trials. In the preliminary experiment, geometric mean cumulative egg counts in the globin group were reduced by 52% and total worm burdens were reduced by 28%, compared to the controls. In the first field trial cumulative faecal egg counts were reduced by 63% in the vaccinated calves. However, the reduction in faecal egg output in these two experiments was not statistically significant and no reduction in faecal egg counts was observed in the vaccinated animals in the two last field trials. In conclusion, vaccination of calves with O. ostertagi globin resulted in highly variable protection levels after challenge infection.

Simple non-invasive prenatal detection of Hb Bart's disease by analysis of fetal erythrocytes in maternal blood

OBJECTIVE

To investigate a simple non-invasive technique for early detection of Hemoglobin (Hb) Bart's disease.

METHOD

Maternal blood smears from 8 known Hb Bart's pregnancies and 40 at-risk pregnancies were investigated. Maternal peripheral blood smears were stained with fluorescence-labeled monoclonal antibodies against alpha- and embryonic zeta-globin chains.

RESULTS

Fetal nonnucleated red blood cells, stained with anti-zeta but not with anti-alpha globin antibodies were found in 15 out of 16 affected pregnancies but were not detected in 23 out of 24 unaffected pregnancies.

CONCLUSION

Results showed that non-invasive immunofluorescence staining of maternal blood is a feasible approach for screening Hb Bart's disease before ultrasound manifestation in affected pregnancies.

Yolk sac-derived primitive erythroblasts enucleate during mammalian embryogenesis

The enucleated definitive erythrocytes of mammals are unique in the animal kingdom. The observation that yolk sac-derived primitive erythroid cells in mammals circulate as nucleated cells has led to the conjecture that they are related to the red cells of fish, amphibians, and birds that remain nucleated throughout their life span. In mice, primitive red cells express both embryonic and adult hemoglobins, whereas definitive erythroblasts accumulate only adult hemoglobins. We investigated the terminal differentiation of murine primitive red cells with use of antibodies raised to embryonic beta H1-globin. Primitive erythroblasts progressively enucleate between embryonic days 12.5 and 16.5, generating mature primitive erythrocytes that are similar in size to their nucleated counterparts. These enucleated primitive erythrocytes circulate as late as 5 days after birth. The enucleation of primitive red cells in the mouse embryo has not previously been well recognized because it coincides with the emergence of exponentially expanding numbers of definitive erythrocytes from the fetal liver. Our studies establish a new paradigm in the understanding of primitive erythropoiesis and support the concept that primitive erythropoiesis in mice shares many similarities with definitive erythropoiesis of mammals.

Sensitivity and Specificity of the Identification of Fetal Cells in Maternal Blood by Combined Staining with Antibodies against Beta-, Gamma- and Epsilon-Globin Chains

OBJECTIVES

Antibodies against fetal and embryonic hemoglobins may identify fetal cells in maternal blood. Both gamma- and epsilon-globins are used as fetal cell markers. Gamma-globin is not fetus specific. So far epsilon-globin has been claimed to be fetus specific. In this communication, we compare the specificity of anti-epsilon- and anti-gamma-globin staining when combined with staining for beta-globin.

METHODS

We applied single and double color immunofluorescent staining techniques in combination with XY chromosome hybridization. The blood sample was taken after chorion villus biopsy at 11 weeks of gestation from a woman carrying a male fetus.

RESULTS

By gamma-globin staining alone, 21 fetal and 2 maternal nucleated red blood cells (NRBCs) were identified. Only 1 of the 2 maternally derived NRBCs expressed beta-globin. By epsilon-globin staining, 92 additional fetal NRBCs were identified.

CONCLUSIONS

Epsilon-globin antibody and combined epsilon- and gamma-globin antibody staining of a blood sample from a pregnant woman at 11 gestational weeks showed higher sensitivity but lower specificity for the fetal origin of erythroblasts with combined compared with separate staining. The final decision of the origin of cells was made by gender determination by FISH. Out of 2 gamma-positive maternal cells 1 was beta-globin antibody positive, 1 was beta-globin negative, indicating that 100% specificity for fetal origin could not be obtained by combining all 3 hemoglobin types. Although only 1 blood sample was tested and only 2 gamma-positive maternal NRBCs were identified, the result indicates that beta-hemoglobin does not discriminate completely between gamma-positive NRBCs of fetal and maternal origin.

A globin in the nucleus!

Cytoglobin and neuroglobin are recently discovered members of the globin family. In situ hybridization localized neuroglobin mainly in brain and retina, while cytoglobin was expressed ubiquitously in all analyzed tissues. In the present study, polyclonal antibodies were raised against both proteins and the distribution of them was studied by immunocytochemistry at tissue and subcellular level. Cytoglobin immunoreactivity was uniformly distributed and found in all tissues studied. At the subcellular level, cytoglobin immunoreactivity was exclusively detected in the cell nucleus. In contrast, neuroglobin immunoreactivity was detected in specific brain regions with varying intensities and in the islet of Langerhans in the pancreas. The immunoreactivity was restricted to the cytoplasm of neurons and endocrine beta cells. The nuclear localization of cytoglobin opens new perspectives for possible function(s) of globin-folded proteins as transcriptional regulators.

Serum antibodies to lipophilin B detected in late stage breast cancer patients

Lipophilin B mRNA is overexpressed in approximately 70% of breast tumors and shows a high degree of correlation with the mRNA expression profile of mammaglobin. This is further supported by the recent finding that, like other members of the secretoglobulin-uteroglobin family, mammaglobin and lipophilin B form a heteroduplex. The studies described show that there are pre-existing antibodies to lipophilin B peptide in the sera of breast cancer patients with different stages and grade of tumor and that this response is different from that seen to recombinant mammaglobin and native mammaglobin-lipophilin B complex. The highest titers were observed in later stage tumors. In addition, low levels of antibody were also seen in some patients with prostate and ovarian cancers, consistent with lipophilin B mRNA expression in these tumors at lower abundance than in breast tumors. In contrast, lipophilin B antibodies were absent in 20 healthy donor sera and 30 lung cancer sera. A polymorphism identified in Lipophilin B did not appear to influence human sera reactivity. The data indicate that humoral immune responses to lipophilin B may serve as a diagnostic indicator, particularly for breast cancer.

Globin attenuates the innate immune response to endotoxin

Hemoglobin is an endotoxin (lipopolysaccharide; LPS)-binding protein that synergistically increases the release of proinflammatory cytokines from the innate immune system in response to LPS. It has been suggested that this activity of hemoglobin facilitates the recognition of Gram-negative bacteria in a wound, thereby maximizing immune efficiency. This synergy may be important to the pathogenesis of a broad spectrum of clinical conditions because elevated hemoglobin levels frequently are observed in patients after the transfusion of red cells, trauma, cardiopulmonary bypass surgery, hemolysis, in addition to other disorders. To determine the molecular basis of the specific hemoglobin-LPS synergy, in this article we tested the effects of globin itself on macrophage responses to LPS. Paradoxically, these studies revealed that globin suppressed tumor necrosis factor (TNF) synthesis in LPS-stimulated murine and human macrophage cultures. LPS comigrated with globin on non-denaturing electrophoretic gels, giving direct evidence for binding. Globin specifically inhibited LPS activity in the standard Limulus assay but did not inhibit interleukin-1beta-mediated TNF synthesis. Iron supplementation of macrophage cultures significantly increased interleukin-1beta-induced TNF release. Intraperitoneal administration of globin protected mice against both LPS-induced lethality and experimentally induced bacterial infection. Thus, the heme-iron moiety of hemoglobin, and not the binding of LPS to globin, enhanced macrophage responses to LPS.

Cross-sensitization to haptens: formation of common haptenic metabolites, T cell recognition of cryptic peptides, and true T cell cross-reactivity

To analyze T cell cross-reactivity to para-compounds, we established CD4(+) T cell hybridomas from mice immunized with adducts of self-globin and one of three different para-compounds: p-aminophenol, p-phenylenediamine, or Bandrowski's base. Some of the hybridomas obtained reacted not only to the immunizing antigen, but also to metabolically related para-compounds, bound to the same protein, thus suggesting formation of common metabolites. Other hybridomas cross-reacted to globin adducts of metabolically unrelated para-compounds, which denotes them as truly cross-reactive cells whose TCR failed to distinguish among the different haptens. One of these hybridomas also reacted against a non-haptenated, cryptic peptide of hemoglobin but not to the full-length native protein. As this hybridoma reacted even more strongly to the respective peptide after it was haptenated, recognition of the native, cryptic peptide was apparently due to true cross-reactivity. To conclude, true T cell cross-reactivity to haptens does occur, as well as the formation of a common reactive metabolite, and T cell recognition of cryptic self-peptides may underlie cross-sensitization to chemicals.

Mammaglobin is found in breast tissue as a complex with BU101

The mammaglobin gene has been shown to be preferentially expressed in breast tissue. Few genes match its specificity. Mammaglobin has generated much interest, and studies are ongoing to develop diagnostic tests for breast cancer based on the detection of mammaglobin. While searching the Incyte Genomics Lifeseq database for tissue-specific markers, we observed a second secretoglobin, BU101, also known as lipophilin B. We report here that mammaglobin, in breast tissue, is found as a complex with BU101. The complex was isolated from breast cancer tissue and was characterized as the biologically relevant form of mammaglobin.

Embryonic and fetal globins are expressed in adult erythroid progenitor cells and in erythroid cell cultures

The understanding of human hemoglobin ontogeny during development is of biological and clinical importance. Molecular and immunocytological techniques were used to study the expression of embryonic zeta (zeta), epsilon (epsilon), and fetal gamma (gamma) globin genes in newborn cord blood, peripheral blood from men, pregnant and non-pregnant women, and in vitro mononuclear cell cultures. We have shown that embryonic and fetal globin mRNA and peptides are expressed in cultured erythroid cells and in circulating blood cells from newborns, adult non-pregnant women and from men. The findings suggest that during erythroid cell differentiation in newborns and adults, there is a transient recapitulation of sequential globin chain expression as found during embryonic and fetal development. Furthermore, these findings underscore the need for caution in using embryonic and fetal globin chains as markers to identify erythroid cells of fetal origin in maternal circulation for prenatal diagnosis.

Improved specificity of NRBC detection in chorionic villus sample supernatant fluids using anti-zeta and anti-epsilon monoclonal antibodies

OBJECTIVE

Fetal erythrocytes leak from fetal capillaries at the time of chorionic villus sampling (CVS). It has been reported that in approximately 60% of CVS cases fetal nucleated red blood cells (NRBC) can be isolated from the supernatant fluid by immunophenotyping with monoclonal antibody (Ab) against the gamma-chain of fetal hemoglobin and used as an additional source for confirmation of the fetal karyotype. However, the increased prevalence of beta-thalassemia mutations in countries such as Greece results in many pregnant women who produce gamma-positive cells. This makes it difficult to distinguish between the fetal and maternal origin of the NRBC. Use of Abs against embryonic hemoglobin chains zeta and epsilon may increase specificity for fetal NRBC detection.

METHODS

Mouse monoclonal Abs against Hb-zeta and Hb-epsilon were used in order to examine if specificity for fetal NRBC detection in CVS supernatant fluids could be improved. 41 samples were studied using anti-zeta and 20 using anti-epsilon monoclonal Abs.

RESULTS

Anti-zeta or anti-epsilon positive erythrocytes were, respectively, identified in 52 of 61 CVS samples and anti-zeta or anti-epsilon positive NRBC were present in all cases. The mean number of Hb-positive erythrocytes identified with the anti-zeta Ab was 58 and the mean number of NRBC 29. The mean number of anti-epsilon positive erythrocytes was 30 and of NRBC 23. FISH with X and Y chromosome specific probes was performed in 26 cases and the results were concordant with the CVS karyotype. Statistical analysis using the correlation test showed that anti-zeta and anti-epsilon were more specific for the detection of embryonic NRBCs.

CONCLUSIONS

Since embryonic monoclonal Abs show increased specificity, they should be preferentially used for NRBC detection in CVS supernatant fluids. Furthermore, the increased specificity of anti-zeta and anti-epsilon Abs may considerably improve prenatal diagnosis from fetal cells isolated from maternal circulation.

Immunization with a synthetic peptide conjugate derived from the N-terminal sequence of either the beta-chain of haemoglobin or the immunosuppressive protein (reOLT 4) reduces the litter size of pregnant rats

A synthetic peptide conjugate based on the N-terminal sequence of a 10 000 MW immunosuppressive serum protein (reOLT 4) was used to immunize female Lewis rats prior to mating, in order to determine whether blocking this protein had an effect on pregnancy. The N-terminal sequence of (reOLT 4) has close sequence homology to the beta-chain of rat haemoglobin so a peptide conjugate based on the N-terminal sequence of this protein was also used to immunize female Lewis rats. Controls included animals that were not immunized and animals that received the peptide carrier, diphtheria toxoid (DT). No statistical differences were found in gestation time or litter sizes in these groups. Differences were, however, evident between these groups and animals that received DT-(reOLT 4) (group 4) or the DT-beta-chain haemoglobin (group 5). There were no statistical differences in litter size or gestation time for group 4 when compared with group 5. Enzyme-linked immunosorbent assay and dot-blot analysis revealed that rats from both groups also had strong responses against DT, the peptide conjugate they were immunized with and the corresponding full-length protein. In both cases, animals from group 4 and group 5 had weak responses to the peptide that they did not receive, together with lower erythrocyte counts and haematocrits, and elevated heart to body weight ratios. Additionally, antibody purified on a (reOLT 4) immunoaffinity column was capable of binding to rat erythrocytes. A second investigation comparing anaemia prior to fertilization and maintained anaemia over the gestation period revealed that only the latter was capable of decreasing litter size to the same degree as obtained for groups 4 and 5. We conclude that for groups 4 and 5 it is the autoimmune effect of continual anaemia over the gestation period, mediated by autoantibodies, which results in the observed lower litter size.

Fetal nucleated erythrocytes (NRBCs) in chorionic villus sample supernatant fluids: an additional source of fetal material for karyotype confirmation

Fetal erythrocytes leak from the fetal capillaries at the time of chorionic villus removal. The purpose of this study was to determine if fetal nucleated erythrocytes (NRBCs) could be isolated from the chorionic villus sampling (CVS) supernatant fluid and used as an additional source of fetal material in order to confirm the fetal karyotype in cases of CVS mosaicism. One hundred CVS supernatant fluids were studied by simultaneous immunophenotyping, using a mouse antifetal haemoglobin antibody, UCH gamma, combined with fluorescent in situ hybridization (FISH) analysis using X- and Y-specific DNA probes. A chromosome 18 probe was also used in the case of a known male fetus with trisomy 18. Fetal haemoglobin (HbF)-positive cells were identified in 73 supernatant fluids and HbF-positive nucleated cells were present in 60 samples. The number of cells detected per sample showed great variation among the individual samples. FISH analysis was performed in 41 cases. FISH prediction of the fetal gender was concordant with the CVS karyotype in all cases, and the fetal trisomy 18 was correctly verified. In five cases in which Y sequences were detected, a small number of HbF-positive cells with two X signals were also identified; interestingly, in three of the five cases, the mother was a beta-thalassaemia carrier. This technique can be used as a quick and accurate method for the immediate verification of CVS results in cases of mosaicism, thus avoiding second-trimester amniocentesis.

Improved fetal nucleated erythrocyte sorting purity using intracellular antifetal hemoglobin and Hoechst 33342

Fetal nucleated erythrocytes (FNRBC) flow sorted from maternal peripheral blood, using monoclonal antibodies (mAb) that bind fetal cell surface antigens, are a noninvasive source of fetal DNA for prenatal diagnosis. These mAbs, however, also bind antigens shared by maternal cells. In sorted populations, this results in maternal cell contamination and low fetal cell purities, which complicates genetic analysis by fluorescence in situ hybridization (FISH) and polymerase chain reaction (PCR). Fetal hemoglobin, (alpha 2 gamma 2), has been proposed as a useful fetal marker. To improve fetal cell enrichment from maternal blood, we developed an intracellular staining protocol that combines anti-gamma mAb with Hoechst 33342 to identify and flow sort FNRBC. Artificial mixtures of male umbilical cord cells (as a source of fetal hemoglobin) and female adult, non-pregnant peripheral blood mononuclear cells were stained and flow sorted using this protocol. FISH analysis was performed using chromosome X and Y specific probes. Fetal cell purities were calculated by microscope confirmation of anti-gamma staining and counting the number of X and Y signals present after FISH. Results from microscope analyses showed a fetal cell yield of 39-100% and fetal cell purities of 59-73%. These purities are significantly higher than the .001-4.8% previously reported by us in maternal samples using cell surface staining protocols. FISH results demonstrated that 83-100% (mean = 98%) of anti-gamma positive cells were male, whereas 82-100% (mean = 92.5%) of anti-gamma negative cells were female. These results confirmed that the anti-gamma mAb is highly fetal specific. When applied to maternal blood samples, this protocol should lead to increased sensitivity for prenatal diagnosis.

Isolation, characterization and immunolocalization of a globin-like antigen from Ostertagia ostertagi adults

Western blot analysis using an anti-globin rabbit serum Rb94 revealed a major band of 17 kDa in extracts of Ostertagia ostertagi adults and 4th-stage larvae. The adult stage globin-like antigen (OoAdGlb) was purified from total worm extracts by liquid chromatography. The protein has an estimated molecular mass of 36 kDa under non-reducing conditions, suggesting a dimeric structure containing 2 non-covalently linked 17 kDa monomers. Tryptic peptides were sequenced and showed strong similarities with the globins of free-living and parasitic nematodes. Immunolocalization revealed the presence of this globin-like antigen in the body wall musculature and/or the cuticle of O. ostertagi adults. An enzyme-linked immunosorbent assay based on the purified OoAdGlb showed no differences in response between calves infected by O. ostertagi and/or Cooperia oncophora and the negative controls.

T cell recognition of Tn-glycosylated peptide antigens

The mouse hemoglobin-derived decapeptide Hb (67-76), VITAFNEGLK, which binds well to Ek and is non-immunogenic in CBA/J mice, was O-glycosylated with the tumor-associated carbohydrate Tn (alpha-D-N-acetylgalactosamine, or alpha-D-GalNAc). Each of the ten positions in the peptide was substituted with serine or threonine having the Tn antigen attached. The complete set of Tn-glycosylated peptides were then studied for binding to Ek and for immunogenicity in CBA/J mice. All of those glycopeptides which had the Tn attached to serine or threonine at a position in the peptide where, according to the crystal structure determinations, the amino acid side chain was oriented downwards into the binding site of the major histocompatibility complex (MHC) molecule, completely lost their capacity for binding to Ek. This was the case for the glycopeptides with Tn attached at position 68 and 76, which are the major anchor residues and for those with Tn attached at position 71 and 73, which function as secondary anchor residues. Those glycopeptides which had Tn attached to serine or threonine at positions where the side chain pointed away from the binding site maintained their capacity for binding to Ek, except for those with Tn attached at position 70 and 74. Furthermore, some of the MHC-binding glycopeptides were immunogenic. In particular, this was the case for the glycopeptide with Tn attached to the central position 72 in the decapeptide. From previous studies, this is known to be the dominant T cell receptor contact residue of Hb (67-76). The results suggest that T cells may be capable of recognizing epitopes which are partially defined by a small glycan group.

Rare event selection of fetal nucleated erythrocytes in maternal blood by flow cytometry

A noninvasive method of prenatal genetic diagnosis requires fetal cell selection from the maternal circulation that allows efficient recovery for analysis by fluorescence in situ hybridization (FISH). We have solved several problems that negatively affect the isolation and FISH analysis of fetal nucleated red blood cells (nRBCs) in the maternal circulation. The use of glycophorin A (Gly A) antibodies (Abs) for selection is problematic because all five monoclonal antibodies (mAbs) tested caused agglutination of non-nRBCs, thereby changing both light scatter and fluorescence properties of cells by flow cytometry. Because the number of non-nRBCs is variable after Ficoll separation, isolation of nRBCs could be compromised severely by agglutination of nucleated cells with nonnucleated cells, causing them to shift light scatter and fluorescence properties. Several methods for the removal of unwanted maternal white blood cells with CD45 mAbs were also evaluated. Magnetic bead depletion was found to interfere with FISH detection because of residual bead debris after sorting. By contrast, removal of CD45+ cells by a panning technique eliminated this problem. Positive selection methods based on CD71, CD45, and LDS-751 staining and detection of fetal cells by gamma globin expression were also analyzed. Fetal cells were detected by FISH in 11 of 19 (CD71 selection) and in 13 of 15 (gamma selection) random pregnancies. These data support the possibility of a noninvasive method for isolation and analysis of fetal cells for prenatal diagnosis.

Determinants of carboxyl-terminal domain translocation during prion protein biogenesis

The prion protein (PrP) displays some unusual features in its biogenesis. In cell-free systems it can be synthesized as either an integral transmembrane protein spanning the membrane twice, with both amino and carboxyl domains in the lumen of the endoplasmic reticulum, or as a fully translocated polypeptide. A charged, extracytoplasmic region, termed the Stop Transfer Effector (STE) sequence, has been shown to direct the nascent translocating chain to stop at the adjoining hydrophobic domain to generate the first membrane-spanning region (TM1). However, the determinants of the second translocation event in the biogenesis of the transmembrane form have not been identified previously. Moreover, the relationship of transmembrane and fully translocated forms of PrP has not been well understood. Here, we report progress in resolving both of these issues. Using protein chimeras in cell-free translation systems and Xenopus oocytes, we identify the sequence which directs nascent PrP to span the membrane a second time, with its carboxyl-terminal domain in the endoplasmic reticulum lumen. Surprisingly, PrP carboxyl-terminal domain translocation does not appear to be directed by an internal signal or signal-anchor sequence located downstream of TM1, as would have been expected from studies of other multispanning membrane proteins. Rather, carboxyl-terminal domain translocation appears to be another consequence of the action of STE-TM1, that is, the same sequence responsible for generating the first membrane-spanning region. Studies of an STE-TM1-containing protein chimera in Xenopus oocytes demonstrate that most of these chains upon completion of their translation, initially span the membrane twice, with a topology similar to that of transmembrane PrP, but are carbonate-extractable. These chains have the transmembrane orientation only transiently and chase into a fully translocated form. These results support a model in which a metastable "transmembrane" intermediate, residing within the aqueous environment of the translocation channel, can be converted into either the integrated transmembrane or the fully translocated form of PrP, perhaps directed by trans-acting factor (s). Such a model may explain why stable the transmembrane isoform of PrP has not been observed in normal cells and how nascent PrP might be directed to alternate pathways of folding.

Detection of the (--SEA) double alpha-globin gene deletion by a simple immunologic assay for embryonic zeta-globin chains

Homozygous alpha-thalassemia [alpha-thal-1], with loss of all four alpha-globin genes, causes lethal hydrops fetalis. The most common mutation producing this syndrome is the Southeast Asian (--SEA) double alpha-globin gene deletion. Erythrocytes from adults heterozygous for the (--SEA) deletion have minute amounts of embryonic zeta-globin chains detectable by anti-zeta-globin monoclonal antibodies. Among 225 peripheral blood samples tested by a simple anti-zeta-immunobinding tetrazolium dye test, 81 were positive and 144 were negative. The majority of subjects were of Filipino, Chinese, or Laotian ancestry. All 81 positive samples were confirmed by Bam HI digests and a zeta-cDNA probe to have the (--SEA) mutation. The (--SEA) double alpha-deletion was the only abnormality in 58. In the others, it was combined with alpha-globin or beta-globin mutations, or coincidental iron deficiency. Four other samples from (--SEA) heterozygotes were negative by this immunologic assay. Anti-zeta negative samples included 78 deletions of the total alpha-globin region, (--Tot), 23 single alpha-globin deletions, and a variety of beta-globin mutations; 16 normocytic samples with normal alpha-genes were also negative. Ten anti-zeta positive and 25 anti-zeta negative samples had benign triplicated zeta-globin genes. In this population, the sensitivity of this test was 95%; and specificity for the (--SEA) mutation was 100%. Anti-zeta immunobinding testing provides rapid, simple, and reliable screening for the (--SEA) double alpha-globin deletion, although it does not detect the (--Tot) total alpha-deletions.

Differences in erythropoiesis in normal chicken and quail embryos

Using antibodies against the fetal and adult forms of alpha- and beta-globin, it has been shown that erythropoiesis in the para-aortic foci (PAF) constitutes a major species-specific difference between chicken and quail embryos. In quail embryos, para-aortic foci are rare, small and rather heterogeneous with regard to their erythropoietic and haemopoietic cell composition. In contrast, the PAFs in chicken embryos are abundant and consist of large numbers of erythropoietic cells. In both species a time difference (approximately 1 day) is observed between the first expression of the fetal alpha- and beta-globin and the adult alpha- and beta-globin in erythropoietic cells. Adult erythropoiesis in both species can be detected first in the stalk of the yolk sac; this is similar to the situation in mammalian and amphibian species. From this time onward the number of circulating adult erythrocytes increases steadily. Whereas in chicken, large intraembryonic foci that can serve as sources for these adult cells arise concomitantly, no such foci can be detected in quail embryos, suggesting that the quail yolk sac is a major source for these adult red blood cells.

Isolation, characterization, and immunoprecipitation studies of immune complexes from membranes of beta-thalassemic erythrocytes

beta-Thalassemia, a hemoglobinopathy that results in the precipitation of denatured alpha-globin chains on the membrane, is characterized by erythrocytes with significantly reduced lifespans. We have demonstrated previously that hemoglobin denaturation on the membrane can promote clustering of integral membrane proteins, and that this clustering in turn leads to autologous antibody binding, complement fixation, and rapid removal of the cell by macrophages. To evaluate whether this pathway also occurs in beta-thalassemic cells, we have isolated and characterized the immune complexes from the membranes of these cells. We observe that autologous IgG-containing complexes obtained by either immunoprecipitation or simple centrifugation of nondenaturing detergent extracts of beta-thalassemic cell membranes contain globin, band 3, IgG, and complement as major components. Absorption spectra of these complexes demonstrate that the globin is, indeed, mainly in the form of hemichromes. Immunoblotting studies further show that much of the band 3 protein in the aggregates is covalently cross-linked to a dimeric or tetrameric form, consistent with the preference of the autologous IgG for clustered band 3. Although the insoluble aggregates constitute only approximately 1.6% of the total membrane protein, they still contain 27% of the total IgG and 35% of the total complement C3 on the thalassemic cell surface. Because cell surface IgG and complement component C3 are thought to trigger removal of erythrocytes from circulation, the hemichrome-induced clustering of band 3 may contribute to the beta-thalassemic cell's shortened lifespan.

The isolation, characterization and cloning of a globin-like, host-protective antigen from the excretory-secretory products of Trichostrongylus colubriformis

An 18-kDa component from the excretory-secretory (ES) products of adults of Trichostrongylus colubriformis was isolated and characterized, and was shown to induce 60-84% protection of guinea pigs from challenge infection following a single intraperitoneal injection. Amino-terminal sequence analysis of gel-purified protein enabled oligonucleotides to be synthesized and used to screen a lambda gt10 cDNA library made from young adult worm mRNA, and to synthesize full-length clones from cDNA using the polymerase chain reaction (PCR). The full-length clones coded for a 20-kDa precursor protein of 173 amino acids which had a strongly hydrophobic leader sequence of 15 residues. The mature protein sequence of 158 amino acid residues was rich in charged amino acids (32%), including 8 oppositely charged pairs of amino acids. The protein sequence contained no half-cystine residues and no potential N-glycosylation sites. Unlike 2 other fully characterized ES components which are expressed only in the parasitic stages, mRNA coding for the 20-kDa component was present in both the parasitic and free-living stages of T. colubriformis. The parasite protein had approximately 20% identity with globins from human and from the larvae of the insect Chironomus thummi thummi. The homology included the invariant distal histidine and phenylalanine, and a number of other residues highly conserved in globins.

Quantities of adult, fetal and embryonic globin chains in the blood of eighteen- to twenty-week-old human fetuses

The prenatal diagnostic program, established at Hacettepe University in Ankara for the purpose of detecting beta-thalassemia (beta-thal), sickle cell anemia (SS), and Hb S-beta-thal, offered the opportunity of evaluating the relative quantities of adult (beta A, beta S), fetal (G gamma, A gamma, A gamma T), and embryonic (epsilon, zeta) chains in 26 fetuses, aged 18-20 weeks. Methodology involved micro high-performance liquid chromatographic (HPLC) procedures and immunology using an mAb, specific for the embryonic epsilon chain. A good correlation was observed between the beta/gamma in vitro chain synthesis ratio and the level of beta A and/or beta S chains determined by reversed-phase HPLC; the combination of these two sets of data strengthens the prenatal diagnostic approach of detecting beta-thal major but not beta-thal trait. The levels of the different gamma chains were about as observed in newborn babies; the frequency of the A gamma T variant in the 26 fetuses was the same as observed for a larger group of Turkish newborn babies. The level of the embryonic zeta chain was higher than seen in full-term babies and varied between 0 and 1.3%; 5 of the 26 fetuses showed the complete absence of zeta. The embryonic epsilon chain was not detectable, not even in babies with beta-thal major. These data indicate that the synthesis of epsilon is completely turned off in fetuses at the age of 18-20 weeks, while that of zeta continues, albeit at a low level.

A novel monoclonal antibody based diagnostic test for alpha-thalassemia-1 carriers due to the (-SEA/) deletion

The presence of minute amounts of embryonic zeta-globin chains in adult hemolysates is a marker for carriers of alpha-thalassemia-1 resulting from (--SEA/) deletion. Recently, we developed a murine monoclonal antihuman embryonic zeta-globin chain antibody, 8E8. By using this antibody, we have now established a slot-blot immunobinding assay for the rapid detection of zeta-globin chains in adult hemolysates. zeta-globin chains were found to be present in 30 blood samples obtained from individuals who were carriers of alpha-thalassemia-1. In another 30 blood samples from individuals who were not carriers of the (--SEA/) deletion, zeta-globin chains were not detected. This simple diagnostic test can be used in appropriate populations to identify those couples at risk of conceiving fetuses afflicted with the Hb Bart's hydrops fetalis syndrome due to homozygous alpha-thalassemia.

Quantitation of protein adducts as a marker of genotoxic exposure: immunologic detection of benzo[a]pyrene--globin adducts in mice

Immunologic methods have been developed for the determination of benzo[a]pyrene (BP)-protein adducts and validated in animals treated with [3H]BP. A previously developed antibody, 8E11, which recognizes 7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10- tetrahydrobenzo[a]pyrene (BPDE-I)-modified DNA or protein as well as BPDE-I-tetraols, was used. The sensitivity of the assay was increased by enzymatic digestion of the modified protein with insoluble protease into peptides and amino acids before analysis. In a competitive enzyme-linked immunosorbent assay (ELISA) with digested BPDE-I-modified bovine serum albumin, 50% inhibition occurred at 400 fmol of adduct compared to 1450 fmol for the non-digested albumin. Analysis of globin (Gb) isolated from animals treated in vivo with 0.3-3 mg [3H]BP indicated that the ELISA could detect 90-100% of the adducts determined by radioactivity. Levels of adducts in lung and liver DNA and serum albumin were correlated with the levels of Gb adducts. Of the total radioactivity associated with hemoglobin, only less than or equal to 10% was from Gb while approximately 80% was from the heme fraction and the remainder from free BP metabolites. Significant cross-reactivity of antibody 8E11 was found with several BP-diols and phenols, suggesting that the immunoassay will not only be specific for BPDE-I adducts but will also detect adducts of other BP metabolites as well as other aromatic hydrocarbon diol epoxides. An immunoaffinity column of antibody 8E11 coupled to Sepharose 4B was used to isolate modified peptides from the digested Gb. About 65% of the applied radioactivity was retained on the column. Between 1 and 2 mg of non-modified digested Gb could be added to the sample without interfering with binding of adducts. Protein digestion and immunoaffinity chromatography should be useful for the measurement of protein adducts in biomonitoring studies.

Direct evidence for functional self-protein/Ia-molecule complexes in vivo

Through the development of a panel of murine hybridomas reactive to murine hemoglobin, we have been able to study the processing and presentation of self antigens by antigen-presenting cells. Our results demonstrate that peritoneal macrophages in vivo can process and potentially present the self-antigen hemoglobin. We have extended this finding to show that, directly after removal from the mouse, antigen-presenting cells from a variety of tissues stimulate our hemoglobin-specific hybridomas without any manipulation or addition of exogenous antigen. This constitutes direct functional proof that in a nondisease state self proteins are processed constitutively and can be presented in a fashion similar to that in which foreign antigens are presented. Our demonstration that antigen-presenting cells can process and potentially present self as well as foreign molecules implies that self-tolerance occurs at the level of the T cell. This constitutive processing and presentation of self antigens has potentially far-reaching implications in self-tolerance, autoimmunity, and alloreactivity.

An immunoassay to detect human embryonic epsilon globin chains by a murine monoclonal antibody

Human embryonic epsilon globin chains were isolated from lysates of cultured human leukemic K562 cells induced with hemin. Mice were immunized with epsilon globin chains, and a murine hybridoma cell line was established that secreted monoclonal anti-epsilon globin antibody. A sensitive and specific slot blot immunoassay for epsilon globin chains has been developed. epsilon Globin chains were shown to be present in hemolysates from fetuses of 20 weeks' gestation but were not detected in normal cord blood hemolysates. This immunoassay is useful for the study of epsilon globin ontogeny during embryonic and fetal development as well as for searching for inappropriate epsilon globin chain expression in hematologic disorders resulting from genetic abnormalities or neoplastic processes.

Characterization and comparative immunoreactivity of antibody to newt (T. cristatus) globins

Rabbit antisera to newt (T. cristatus) globin were produced by repeated injections of globin and antiglobin antibodies purified by chromatography on globin-Sepharose 4B. Ouchterlony and SDS PAGE analysis indicated that the material eluted from the affinity column was rabbit IgG. The antiglobin antibodies tested by immunodiffusion and ELISA cross-reacted with native hemoglobin and globin from T. cristatus and to varying extents with globins of N. viridescens, R. pipiens and X. laevis, but not with human globin. The degree of cross-reactivity appeared to parallel the evolutionary relatedness of these species, suggesting common antigenic determinants among globins of various vertebrate species.

Monoclonal antibodies specific for globin chains

Six monoclonal antibodies specific for human globin chains are described. They are produced by stable clones obtained by raising hybridomas using cells of mice immunized with either adult or fetal hemoglobin. Characterization of the antibodies included testing against tetrameric human and other animal hemoglobins, isolated hemoglobin chains, and when indicated, cyanogen bromide fragments. Monoclonals 16-2 and 37-8 are beta-chain specific. Antibody 31-2 recognizes an antigenic determinant common to the alpha and beta subunits. Monoclonal 30-3 recognizes determinants best expressed in the alpha 2 beta 2 tetramer. Antibody 45-1 recognizes a determinant common to beta and gamma subunits, while antibody 51-7 is gamma-chain specific. None of the monoclonal antibodies recognizes mouse hemoglobin, and they display significant differences in binding to hemoglobins of various species. The species-specific reactions and the knowledge of the primary structures of globins allowed deductions about the antigenic sites recognized by two of the monoclonals (16-2 and 45-1). These antihemoglobin monoclonal antibodies will provide useful probes for studying hemoglobin expression in vivo and in vitro.

A new approach for the antenatal diagnosis of beta-thalassaemia: a double labelling immunofluorescence microscopy technique

A new approach to the antenatal diagnosis of beta-thalassaemia major (homozygous beta-thalassaemia) has been developed. Using rhodamine-labelled antibodies directed against gamma-globin, fetal erythrocytes can be identified in fetal blood samples contaminated with maternal cells, and using fluorescein-labelled antibodies directed against beta-globin, the presence of beta-chains (and thus Hb-A) may be determined in the same cells by double labelling immunofluorescence microscopy. The results obtained using this technique on blood samples from fetuses at risk for beta-thalassaemia major show that if fetal beta-chains are detected immunochemically the fetus is normal or heterozygous for beta-thalassaemia and over 85% of the fetuses unaffected by beta-thalassaemia major may be identified in this way. The technique is rapid, applicable to small numbers of fetal erythrocytes heavily contaminated with maternal cells and eliminates the necessity of determining chain synthesis ratios in those cases where beta-chains are detected immunochemically.

Effect of temperature on the red cell membrane protein and its antigenic reactivity

The red blood cell membrane protein pattern of erythrocytes exposed to 50 C for 10 to 15 minutes was found to be abnormal by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. Membranes of heated red blood cells consistently had significant elevation of band 7 and 8. The total membrane protein content (mg/10(9) cells) of heated erythrocytes was increased, but the sialic acid content was normal. Heated erythrocytes showed a consistent decrease in the reactivity of Fya and Jka antigens. Other blood group antigens were variably affected by temperature elevation. These observations may explain the mechanism of antibody elution by heat.

Antibodies to an NH2-terminal fragment of betaS globin. II. Specificity and isolation of antibodies for the sickle mutation

The immunochemical specificity of an antiserum produced to an NH2-terminal 55-residue polypeptide fragment of the betaS globin, betaS(1-55), was analyzed with a radioimmunoassay using the radioiodinated fragment as a tracer. These studies show that most of the antibodies have comparable reactivity with betaS(1-55), betaA(1-55), betaS globin, betaA globin, HbS, and HbA. However, the antiserum contains some antibodies which react only with the species derived from HbS. These "S" -specific antibodies were isolated by absorption of the serum on a column of betaA(1-55) coupled covalently to Sepharose. The S-specific antibodies have markedly diminished reaction with betaA(1-55) and HbA. The S specificity was localized to the valine substitution at position 6 of the beta globin, as shown by inhibition of the binding of the radiolabeled fragment to S-specific antibodies by the synthetic peptide betaS(1-13). These antibodies, which appear monospecific, can be used to study the conformation of the NH2-terminal region of the beta chain of HbS.

Antibodies to an NH2-terminal fragment of betaS globin. I. Preparation and radioimmunoassay

Polypeptide fragments corresponding to the NH2-terminal 55 amino acids of betaS and betaA globins were prepared by cyanogen bromide treatment of globin and isolated by gel filtration on Sephadex G-50. Sheep were immunized with the isolated NH2-terminal fragments, and one of these sheep produced precipitating antibodies to the NH2-terminal fragment of betaS globin. These antibodies also reacted with betaA and betaS globin and hemoglobins A and S, as shown by immunodiffusion and quantitative precipitation studies. A radioimmunoassay was developed using the radioiodinated NH2-terminal fragment as tracer, and dextran-coated charcoal for separating bound and free peptide. The radioimmunoassay was used to characterize the interaction of the antibodies and the NH2-terminal fragment of betaS globin.